答案和详解如下： 1、If the probability of both a new Wal-Mart and a new Wendy’s being built next month is 68 percent and the probability of a new Wal-Mart being built is 85 percent, what is the probability of a new Wendy’s being built if a new Wal-Mart is built? A) 0.70. B) 0.60. C) 0.80. D) 0.85. The correct answer was C) P(AB) = P(A|B) × P(B)
0.68 / 0.85 = 0.80 2、The following table summarizes the availability of trucks with air bags and bucket seats at a dealership.
| Bucket seats | No Bucket Seats | Total | Air Bags | 75 | 50 | 125 | No Air Bags | 35 | 60 | 95 | Total | 110 | 110 | 220 |
What is the probability of randomly selecting a truck with air bags and bucket seats? A) 0.16. B) 0.28. C) 0.57. D) 0.34. The correct answer was D) 75/220 = 0.34. 3、The probability of a new Wal-Mart being built in town is 64%. If Wal-Mart comes to town, the probability of a new Wendy’s restaurant being built is 90%. What is the probability of a new Wal-Mart and a new Wendy’s restaurant being built? A) 0.675. B) 0.240. C) 0.306. D) 0.576. The correct answer was D) P(AB) = P(A|B) × P(B)
The probability of a new Wal-Mart and a new Wendy’s is equal to the probability of a new Wendy’s “if Wal-Mart” (0.90) times the probability of a new Wal-Mart (0.64). (0.90)(0.64) = 0.576. 4、Helen Pedersen has all her money invested in either of two mutual funds (A and B). She knows that there is a 40 percent probability that fund A will rise in price and a 60 percent chance that fund B will rise in price if fund A rises in price. What is the probability that both fund A and fund B will rise in price? A) 0.24. B) 0.40. C) 0.70. D) 1.00. The correct answer was A) P(A)=0.40, P(B|A)=0.60. Therefore, P(A?B) = P(A)P(B|A) = 0.40(0.60) = 0.24 5、Data shows that 75 out of 100 tourists who visit New York City visit the Empire State Building. It rains or snows in New York City one day in five. What is the joint probability that a randomly choosen tourist visits the Empire
State
Building on a day when it neither rains nor snows? A) 95 percent. B) 20 percent. C) 15 percent. D) 60 percent. The correct answer was D) A joint probability is the probability that two events occur when neither is certain or a given. Joint probability is calculated by multiplying the probability of each event together. (0.75) * (0.80) = 0.60 or 60 percent. | 
发表于 2008-4-9 15:07
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